Chennai: The final countdown for the May 8 launch of GSLV-D2, the second developmental flight of India's prestigious Geosynchronous Satellite Launch Vehicle (GSLV), commenced at 1.58 am (IST) on May 7, the Indian Space Research Organisation (ISRO) said.

GSLV-D2, carrying the 1,800-kg GSAT-2, a technology experimental satellite, is scheduled for lift-off at 4.58 pm (IST) on May 8 from the space port at Satish Dhawan Space Centre at Sriharikota, about 100 kms from Chennai.

"The countdown is progressing smoothly, absolutely without any hitches," a spokesman of ISRO said.

GSAT-2 is scheduled to be injected into a geo-synchronous transfer orbit (GTS), 999 seconds after the lift-off.

GSLV-D2 is an advanced version, mainly in respect of the improvements effected on the various stages of the three stage vehicle so as to carry a higher payload.

GSAT-2 weighs 1,800 kg while GSAT-1 carried by GSLV-D1 weighed only 1,540 kg. The satellite has a communication pay load consisting of four C-band transponders, two Ku-band transponders and one mobile satellite service (MSS) equipment.

It also has a technology experimental payload, including radiation dose monitor, surface charge monitor, solar X-ray spectrometer, and coherent radio beacon experiment.

GSAT-2 will be placed on a geosynchronous transfer orbit of 180 km perigee (nearest point to earth) and 36,000 km apogee (farthest point to earth) about 17 minutes after lift off.

The third developmental flight of GSLV is expected to use indigenous cryogenic engines in place of the Russian engines presently being used in GSLV in its third stage. Development of cryogenic engines by ISRO is in an advanced stage according to ISRO sources.

Meanwhile, Union government had already given the green signal for developing GSLV Mk III, a more advanced version of GSLV, which could carry a payload of up to 4,000 kg. It would take at least five to six years for developing GSLV-Mk III.

PTI